Answer
Hyperboloid of one sheet.
See image:
.
Work Step by Step
Comparing to Table 12.1, we recognize the form of
a hyperboloid of one sheet, with the z-axis as the axis.
The intersections with the planes parallel to the xy-plane are circles.
The intersections with the planes parallel to the xz-plane are hyperbolas.
The intersections with the planes parallel to the yz-plane are hyperbolas.
